Semiconductor devices, for example integrated circuits and power semiconductors, typically exhibit an encapsulation for protection. Contact elements comprising contact areas (contact pads) that allow the semiconductor device to make external contact are integrated into the encapsulation. The contacting may be effected, for example, by way of bonding wires. To this end, thin aluminum wires are usually pressed with one of their ends on the bare contact area of the contact element, with the result that they are mechanically deformed and at the same time connected to the top metal layer of the contact element. When bonding, mechanical forces are generated that act on the underlying structures of the semiconductor device and may damage said structures. As miniaturization increases, the thickness of the semiconductor substrates as well as the thickness of the semiconductor devices integrated therein and the layered structures also decreases. Therefore, they are especially sensitive to mechanical stress.
Mechanical stresses also occur when the semiconductor devices heat up, for example, through the dissipation of power while operating the semiconductor device, owing to the varying coefficients of expansion of the individual, interconnected functional layers. Especially in the case of power semiconductors the thermally induced mechanical stresses, for example between the aluminum bonding wires and the silicon substrate and/or between the metallization and the silicon substrate, lead to failures. Furthermore, in particular power semiconductors are subject to a fluctuating thermal stress, which may lead to mechanical stresses.
Mechanical stresses may lead to the formation of cracks inside the individual layers. If the mechanical stress, for example alternating thermal stress, persists, the cracks may extend into other areas of the semiconductor device and have a negative impact on its functionality.